The 300 AAC Blackout (300 BLK, or 7.62x35mm) was created by Advanced Armament Corp. and Remington in order to provide the military with a way to shoot .30 caliber bullets from the M4 platform with only a barrel change. It has since become popular for a wide range of uses including hunting and home defense.

The cartridge shares case-head dimensions and body taper with the .223 Remington. Not only does this allow for compatibility with existing magazines and bolts, but it allows reloaders to form their own brass from cut-down 5.56mm or .223 cases – ensuring brass supply even in the event of a shortage of factory brass.

The 300 AAC Blackout is a similar concept to previous wildcats, such as the 30-221 and 300 Fireball, as well as the proprietary 300 Whisper®, except that 300 BLK was the first to be a SAAMI approved cartridge and any company is free to make firearms or ammunition.

300 AAC Blackout is also finding use with hunters, who may not have been able to legally hunt with .223 in their state, and who prefer .30 caliber bullets for medium-sized game. It provides similar effectiveness to the 7.62×39 or the slightly more powerful 30-30 cartridges except works in the more up-to-date AR15 platform. Effective range for hunting is about 100-150 yards.

Screw JD Jones who sat on his product and refused to share his creation after earning millions. He is a greedy old has been who would have let this cartridge perish. He deserves NOTHING and would tax the IRS if he could do it.

In my 16.5″, X95 Sierra 220 grain RN with 11.2 grains of H110 WILL NOT cycle. In my Palmetto State Armory 7.5″ upper the load functions perfectly ! What could be the problem with the load in the 16.5″ ?

A carbine length gas system (one comment mentioned 16.5 inch gun would not cycle the action) will not work with subsonic loads in 300 blackout. There may be rate exceptions but your in for a lot of frustration if you go that route. You MUST have a pistol length gas system. My TSAR 11.5″ upper is flawless so far.

While the powder formulas are identical, the chrono testing is likely from different production lots. You may have a great load that is pushing max and loading from an 8lb keg, and a few years later you buy another keg. Smart and safe loader will back off the load and work it back up simply due to powder age and lot variation.

I really appreciate the updated data, I was working on subsonic loads and Sierra did the work for me. That’s a lot of work already done that I only need to tweak for my rifle, however when I chrono these loads Sierra is pretty much dead on!
Now for preparations for 2018 Bear season…
Thanks

The data is all wrong anyway. Example 220gr subsonic data there for h4198 and reloader 7… two things…first not in anyway subsonic…they are high velocity. Second stupidly and even dangerously compressed loads…
If you folks want really figures use quick load…this data and noslers data is bogus.
Want a subsonic load using reloader 7 or h4198? Oal 2.260 8.7 grains

So how does everyone find the stability of the heavier projectiles with the 1-8″ twist rate? I have seen a few complaints from people with barrels under 10″, but better stability was found when switching to a 1-7″ twist rate.

I plan to build a bolt action with a 16.5″ barrel and will use projectiles between 180 – 220 gr., so not sure if I should go with the 1-8″ or get a 1-7″ barrel blank made. Any thoughts?

Have experienced some unstability problems with cans and 1:8 barrels with 220 gr sierras. Ordered 1:7 barrel to another gun, used same loads in exactly same conditions, no issues. 220 sierras were stable to 150 meters with 1:7 twist. Instability with 1:8 caused problems with loger cans, bullet maybe wobbling after rifling. Also slight keyholing and groups growing up. Never seen that with 1:7 rifling twist.